Hydraulic transmission



Oct. 17, 1961` G. GARNIER HYDRAULIC TRANSMISSION 5 Sheets-Sheet 1 FiledJuly 9, 1957 24 f Amr l AWI /n venfar l f a J 1 Afforgeys oct. 17, 19611 Filed July 9, 1957 G. GARNlER HYDRAULIC TRANSMISSION 5 Sheets-Sheet 2/n Ven/or GEORGES @ARN/ER B y,

A flarneys Oct. 17, 1961 G GARNIER HYDRAULIC TRANSMISSION 5 Sheets-Sheet3 Filed Jqly 9, 1957 /nvenlor Af/orneys Ot. 17, 1961 G. GARNIER3,004,450

HYDRAULIC TRANSMISSION Filed July 9, '1957 5 Sheets-Sheet 4 GEORGESGAR/WEE' f 9 f l 5) Jaa/Nw .s ,/aulmw..

A llorneys Oct. 17, 1961 G. GARNIER v3,004,450

` HYDRAULIC TRANSMISSION Filed July 9, 1957 5 Sheets-Sheet 5 Fig. 7

GEORGES GAR/WER Alko/ways United States Patent 3,004,450 HYDRAULICTRANSMISSION Georges Garnier, Asnieres, France, nssignor to AirEquipement, Asnieres, Seine, France, a French com- Filed July 9, 1957,Ser. No. 670,793 Claims priority, application France July 25, 1956 1Claim, (Cl. 74 687) The present inventionv relates to hydraulictransmissions having a continuously variable transmission ratio,especially transmissions interposed between a motor or a jet engine ofan aircraft and an apparatus driven by this motor or jet engine and, inparticular, transmissions interposed, for example, between an electricalternator whose speed(output speed of the transmission) must bemaintained constant and a power take-off from the motor or jet engine ofthe aircraft having variable speed (input speed of the transmission).

There have already been proposed for variable-speed hydraulic drives,diilerential arrangements in which there are employed two hydraulicdevices each being formed, for example, by a cylindrical block or bodyin which are movable pistons, the ktravel of these pistons in thecylindrical block being controlled by a displacement relative tosuitable means, for example cam means.

Itis possible to drive in rotation, by means of the input shaft, themeans controlling the pistons or the cylindrical blocker one of thedevices, and, by means of the output shaft, the means controlling thepistons of the cylindrical block of the other device.. Only one of thehydraulic devices is arranged to have aV variable output. In theproposed differential systems there are interconnected one. of the partsof the Vinput device and one of the parts of the output device (forexample, the means controlling the pistons of the input device and themeans controlling the pistons of the output device, the cylindricalblock of the input device and the cylindrical block of the outputdevice, the cylindrical block of the input device and the meanscontrolling the pistons of the output device, or the means controllingthe pistons of the input device and the cylindrical block of the outputdevice), so that when the speeds of the input shaft and the output shaftare equal, no relative movement occurs between the pistons of the twodevices and their respective control means. Asone of the hydraulicdevices is arranged to effect maximum travel and the other no travel, nohydraulic exchange occurs between the two devices other than thatrequired to compensate for leakages between the pistons and thecylindrical blocks, and, by Ymeans of the hydraulic distribution ofvalving between the hydraulic devices, the power is transmittedmechanically from one device to the other owing to a hydraulic lockingof the two devices.Y

YIn this arrangement, eiciency is good when the input and outputspeedsare exactly equal or close to one,

mentioned hydraulic devices, only one of which devices has a variableoutput, atleast two planetary differentials so as to obtain a four-waytransmission through which the hydraulic power transmitted tendsasymptotically toward zero value, on the one hand, when the speed tendstoward zero and, on the other hand when the speed reaches a certainvalue.

But in actual fact there is no point in trying to obtain maximumtransmission eiciency for zero speed, which is of no use in itself andcorresponds to infinite pressure increase in one of the hydraulicdevices and requires regulating means which cancels out this advantage.

One object of the invention is to obtain that transmis-` sion eiiciencybe maximum for the most frequent or usual operational conditions. In thecase of an aircraft motor or jet engine, these conditions correspond toidling speed and the most usual operational speed, namely cruisingspeed. The speeds of the motor or jet engine between the aforementionedtwo speeds are speeds which are not used in a continuous manner, and thesame is true of speeds in excess of cruising speed. Transmission elli-lspeed of said two operational speeds, the.output of the,

tirst device remains maximum whereas the output of the second deviceincreases from zero to maximum, from the mean speed of said two usualoperational speeds to the higher of said operational speeds, the outputof thel rst device decreases from maximum to zero whereas the output ofthe second device remains maximum, and for speeds exceeding the higherof said usual operational speeds, the voutput of the first device isreversed whereas that of the second device remains maximum.

Further features and advantages of the invention will be apparent fromthe ensuing description with reference to the accompanying drawings of atransmission embodying the invention adapted to be interposed between avariable-speed input shaft, for example connected to a power take-off ofan aircraft motor, and a constantspeed output shaft, for example adaptedto drive an alternator, said embodiment being given as an example, andthe invention being in no way restricted to said embodiment.

In the drawings:

FIG. l is an axial sectional view ofga transmission embodying theinvention, taken along line I-I of FIG. 3;

FIG. 2 is an axial sectional View taken along line II-ll of FIG.'3; Y

FIG. 3 is a cross-sectional view taken along line'` Ill-III of FIG. 1,the gears being shown diagrammatically by their pitch circles.

FIG. 4 is a sectional view, taken along line IV--IV FIG. 6 is asectional view of a modification of` the means controlling theinclination of the cams.

FIG. 7 is a diagrammatic view of the general hydrauli circuit.

, ln the embodiment shown in the figures, the hydraulic spec/.l variatorofthe invention comprises two associatedA hydraulic units or devices 1and 2, each of which comf prises a barrel pump of which the cylindricalbloclcor rotor 3 or 4 respectively is carried by a bearing 5 or 6mounted in the case 7 of the transmission. parallel with thetransmission axis and formed in the rotor 3, 4, contain the pistons 10,11 which bear against Bores 8, 9

. 3 a cam 12, 13 through the medium of sliding pads 14, 15. The pads 14,15 are applied against the corresponding cam 12, 13 by a plate 16, 17which bears against a ball journal 18, 19 urged toward the cam 12, 13 bya spring 20, 21 respectively. v

The cam 12, 13 Vis orientable about a journal Z2, 23 carried by the case7. 1

- The rotor 3 of the pump 1 is driven in rotation in its bearing by agear 24' fixed thereto and meshed with a gear 25 of a gear train whichwill be described hereinafter.

' If the cam 12 is given, by the means described here-- inafter, Aacertain inclination relative to the rotor 3 driven in rotation, thepistons will be causedto reciprocate within the bores S and to dischargefluid at a certain output depending on the inclination of said cam 12.

Ports 26 connect the bores of the rotor 3 to a distributing or valvingport plate 27 which communicates with a liquid input port 28 and aliquid output porti@ connected through passageways 101, 102 (FIG. 7) tocorresponding ports 30, 31 of a distributor plate 32 pertaining to thesecond hydraulic device or unit 2.

The rotor 4 of the second hydraulic unit 2 is driven in rotation in'itsbearing 6 by the gear 33 fixed to this rotor and meshed with the gear 34of a gear train described hereinafter.

If the cam 13 is given, bythe means described hereinafter, a certaininclination relative to the rotor 4 driven in rotation, the pistons 11will be caused to reciprocate within the bores 9 and to discharge iiuid`at a certain output depending on the inclination of said cam 13.

- "Ports 35 connect bores 9 ofthe rotor 4 to the distributor plate 32.

. I As. can Abe. seen from. FIG. 4, the cam 12 is constantly urged intoa position of maximum inclination by a piston 36 which moves. in. acylindrical aperture 37 formed in the case 7, and conventionallyconnected through the pipes 103 and 104 (FIG. 7) to the output pressurezonesY of ther hydraulic units so that the pressure of the liquid actsin the chamber 38 behind the piston 36. Further, the cam 13 isconstantly urged into a position of maximum inclination by a piston 39which moves in a cylindrical. aperture 40 formed. in the case 7, andconventionally connected through the pipes 103 and 105 (FIG. 7) to theoutput pressure zones of the hydraulic units so that the pressure of theliquid supplied bythe hydraulic unit 2 acting in the chamber 41 behindthe piston 39. Adjustable abutments 42, 43 limit the pivotal movement ofthe cams 12 and 13 about their respective journals 22 and 23.

A piston 44, to which is fixed a double finger 4S, 46, is adapted todetermine the position of one or the other of the cams 12 or 13 underthe effect of the pressure of the liuid acting ina chamber 47 or 47 of acylinder 48 in which the piston 44 moves. The pressure of the fluid inthe chamber 47 or 47 depends on the position of a slide 49 (see FIG. 5)actuated in conventional manner by a. governor 50 having weights 51.Said slide 49 controls a distributing valve of any known type whichconnects either chamber 47 or 47 to the output pressure zones of thehydraulic units 1 or 2. The fluid under pressure flows, through pipes103, 107, 108 and 109 to both ends of the distributing valve 106 (FIG.7). When the slide 49 is at its right end position, the pressure fluidflows into chamber 47 through' pipe 110, and when the slide 49 is at itsleft end position, the fluid iiows into chamber 47' through pipe 111.The connections are such as to allow admission of the output pressureinto chamber 47 when the speed of the input shaft 56, and therefore ofoutput gear 77, is low, and progressively into chamber 47 when saidspeed increases, so that piston 44 is pushed against the bottom ofchamber 47' at the` as concerns rotation to a variable-speed input shaft56, a planet gear carrier 57 rotatably mounted in anti-frictionbearings, such as ball bearings, S8, 59, a hollow intermediate shaft 60journalled in bearings 61, 62 inside the carrier 57 and carrying thegear 34 which meshes with the gear 33 of the hydraulic device or pump 2and a gear 63 which constitutes the output sun gear of the rstdifferential, and an inner shaft 64 which extends through the hollowshaft 60 and carries at both ends an output gear 65 and the output sungear 66 of the second differential gear train.

The carrier 57 carries two series of planet gears having double teeth,that is, planet gears 67, 68 respectively meshed with sun gears 55 and63, planet gears 69, 70 respectively meshed'with the planet gears 67 andthe sun gear 66.

A train of spur gears comprising gears 71, 72 mounted on acommon shaft73 (see FIG. 5) and gears '74, 75 mounted on a common shaft 76 acts as aspeed reverser to convert the direction of rotation to the oppositedirection in driving gear 77.

The centrifugal governor 50, actuating the distributor valve 49, isdriven by gear 79 which is mounted on the governor shaft andl mesheswith a gear 80 mounted on the shaft 82 of liquid circulating pumps 83and 86, the gear 80 being meshed with the gear 74 of the shaft 76drivingly connected, as explained above, to driving gear 77.

The liquid circulation pump unit 81 comprises the two supply pumps 83,84, the pump 84 being driven by the carrier 57 through the gear 85meshed with the gear 25, and the pump 83 being driven together with adrainage' j pump 86 by gear 74 through gear 80.

The pumps 83, 84, connected in. parallel deliver oil from the feed-tank114 to the suction side of pumps 1 and 2 through the low pressure pipe113, the latter having a branch-pipe 113il towards valve 106. Pump 86returns to tank, 11.4 the oil sucked at the bottom of housing 7throughpipe 115.

The transmission. operates in the following manner:

When the input shaft 56 is driven at a speed lower than or equal. to theidling'speed of the motor, for example at 2000 r.p.m., the slide 49 ofthe governor 50 is in such positionl that the discharge or outputpressure acts in the chamber 47 or 47 ofthe cylinder 48 (see FIG. 4) tobring the piston 44 to the end of its travel, as shown in FIG. 4L Thecam 12 of the device 1 has no inclination owing to the actionl of thefinger 45 of the piston 44. The cam 13, on the other hand, is brought toits position of maximum inclination by the action of the piston 39against which the pressure in the chamber 40 acts. The hydraulic unit. 2therefore tends to discharge at maximum output into the other hydraulicunit 1, but the latter cannot receive this discharge as its output iszero. The hydraulic unit 2 is therefore held or locked stationaryWhereas the unit 1A rotates freely.

v As the unit 2 is held stationary, it also holds the sun gear 63 of thedifferential stationary, through the medium of the gears 33 and 34. Thegears 67, 68, 69 and 70 of the differential, which are engaged with thegear 63v of the shaft 60, therefore cause the gear 66 of the shaft 64 torotate at' the speed of the input shaft 56 multiplied by themultiplication' ratio chosen for this gear train.

The reversing gear' train, consisting of the gears 71, 72, 74, and 75,rotates" the gear 77 of the output shaft 78 at the same speedY as thegear 65 but in the opposite direction.

Meanwhile, the carrier 57 rotates the gear 25 and in consequence thehydraulic unit 1, but this rotation occurs withoutv absorbtion ortransmission of power apart from that necessary to overcome friction,since, as has been explained, this unit 1 has no output.

The multiplication ratio of the gear train is so chosen that the outputshaft 78 rotates at the desired constant Thus the unitLZ starts torotate and allows the gear 63`to rotate, which reduces themultiplication ratio in accordance with the well-known characteristicsof stepdown or step-up planet gears. p A part of the power of the inputshaft 56 continues to be transmitted by the gears S5, 67, 69, 70 and 66to the gear 65 and therefore to the shaft 78 `Another part of this poweris transmitted by the lg'ears168 and 63 to the gears 34 and 33 whichtransmit it to the rotor 4 of the hydraulic unit 2. 'Ifhe lattertransmits this power hydraulically to the unit 1 whichr'eturnsitthroug'h the gears 24 and 25 to the planet gear carrier 57,which in turn returns this power to the gear 66 vdriving the outputshaft through the gears 67, 69 and 70 which act as an ordinarydifferential the principle of which is well known.

/Th'eiacitin of 'thegovernor 50, through the mediumY of the slidel 49controlling the piston 44, adjusts the travel and therefore thedischarge or output of the unit 1 in such manner as to maintain thespeed of the output shaft 78 at the desired constant value.

The power supplied by the input shaft 56 is always fully transmitted,the major part of this power being transmitted directly through thegear, only a minor part being transmitted through the hydraulic units 1and 2.

As the speed of the input shaft increases, the inclination of the cam ofthe hydraulic unit 1 also increases and the proportion of the powertransmitted hydraulically increases until the two units 1 and 2 are atmaximum discharge the unit 2 being always at maximum discharge and theunit 1 reaching this maximum discharge as a result of the displacementof the piston 44 controlled by the slide 49 and the governor 50) Itcould be advantageous to arrange the gears driving the two hydraulicunits in such manner that the units 1 and 2 rotate at this moment at thesame speed, their capacities being then identical and the hydraulicoutput of the transmission being maximum.

At this moment, if the speed of the input shaft 56 continues toincrease, the governor S0 tends to shift the piston 44 toward the end ofthe chamber 48, but the finger 45 then leaves the cam 12 which is heldin abutment by the pressure supplied by the hydraulic units 1 and 2acting in the chamber 38 on the piston 36. On the other hand, the finger46 comes into contact with the cam 13 of the unit 2 and the inclinationof the cam decreases which therefore tends to decrease the output ofthis unit. As the unit 1` remains at constant travel and therefore has aconstant output per rotation, the action of the governor 50, through theslide 49 and the piston 44, adjusts the travel and therefore the outputof the hydraulic unit 2 so as to maintain the speed of the output shaft78 at the desired constant speed.

During this part of the operation, the part of the power of the inputshaft 56 transmitted hydraulically decreases, the hydraulic liow betweenthe two hydraulic units also decreasing.

When the action of the piston 44 controlled by the slide 49 and thegovernor 50 brings,`by means of its finger 46, the cam 13 of the unit 2to its position in which it has no inclination, the unit 1, which is atmaximum output, stops. This unit, which was up to this moment a motor,becomes a pump and tends to discharge Vhydraulically into the unit 2,but the latter cannot receive this discharge as its output is zero, theinclination ofthe cam 13 being maintained zeroby the:l

piston 44.

Thus the hydraulic unit 1 is held stationary as concerns rotation andalso holds the carrier 57 stationary, since the gear 25 is meshed withthe gear 24 of the unit 1.

The rotational axes of the double planet gears 67, 68,

69, and 70 are therefore held stationary and the gear train formed bythe gears 55, 67, 69, i0 and 66 imparts to the gear 65a rotational speedequal to the speed `of the inputV shaft 56.

The shaft 56 and the output shaft 78 therefore rotate at exactly thesame speed, which is the desired constant speed for the output shaft 73.It is advantageous that,

owing to a suitable step-down ratio in the drive of the. input shaft,the speed of the latter be close `to the higher of the two usualoperational speeds (for example, cruising speed of themotor or ofi thejet engine of an aircraft).

Thus there is obtained a completely mechanical drive withouttransmission of hydraulic power.

If the speed of the input shaft continues to increase so` that thegovernor 50 actuates still more the slide 49 controlling thedisplacement of the piston 44, so that the cam 13 of the unit 2 assumesaninclination in the opposite direction to those consideredhereinbefore. The cam 12 of the unit 1 is still at maximum inclinationand the unit 1' once more commences to rotate', but in the opposite"direction to that in which it previously rotated, the unit 1 driving thecarrier 57 through the gears 24 and 25.

The gears of the differential 67, 68, 69 and 70, which are engaged withthe gear 63 of the shaft 64, cause rotation of the planet gear carrier57 in such manner as to reduce the multiplication ratio of the geartrain to obtain the constant speed desired for the output shaft 78.

The power of the input shaft is therefore transmitted partlymechanically and partly hydraulically. In fact, the gears mechanicallytransmit a higher power than that required, the excess power beingreturned to the input shaft through the following operationalconnection: the gear 66 of the shaft 64 of the differential, gears '70,69, 6'7, 68, 63, 34 and 33, the hydraulic unit 2 which discharges intothe hydraulic unit 1, gears 24 and 25, carrier 5'7, gears 67, the excesspower being returned to the gear 55 of the input shaft 56.

FIG. 6 shows a modification of the embodiments of the device controllingthe inclination of the cams, where like reference characters designatelike members of the device shown in FIG. 4. In this modification, thepistons 36 and 39 act on a ball joint S2, 53 unitary with the cams 12,13 respectively, and the piston 44 determines the position of the camsby acting on the rods 54, 55 which are unitary with the pistons 36 and39 and extend into the cylinder 48. The operation of this device is,moreover, identical to that shown in FIG. 4.

Although specific embodiments of the invention have been described, manymodifications and changes may be made therein without departing from thescope of the invention as defined in the appended claim. Thus, thehydraulic units, instead of being barrel pumps, could be pumps ofanother type, such as blade pumps, radial piston pumps or gear pumps.These hydraulic units, instead of being disposed side by side andparallel with the axis of the transmission, could be disposed coaxiallyor concentrically. The device controlling the inclination of the camscould be of another hydraulic type or could even be mechanical; therecould be provided a separate device for each cam. The mounting of thecams could be different from that described and could comprise, forexample, two journals fixed to the transmission case. Instead of havingthe output sun gear of the iirst differential train connected to thecylindrical block of the second hydrauiic device and directly meshedwith one of the teeth of the double planet gears of the firstdifferential, and instead of having the planet gears of the second geartrain meshed with the input sun gear through the medium of the teeth ofthe planet gears of the first train which Vis engaged with said inputsun gear, it could be arrangedv to connect, as concerns rotation, theoutput sun gear of the iirs't train tothe output Shaft andto engage theplanet gears of the second train, whose output gear is connected to thesecond hydraulic unit, with the teeth of the planet gears of the firsttrain which is engaged With the output sun gear of the first train,these last-mentioned teeth having therefore a double Width; this wouldhave for result to' rotate the sun gear connected to the output shaft inthe same direction as the sun gear connected to the input shaft withconsequent elimination of the speed-reversing gears. The planet geartrains Could be of any type, for example they could have an output crowngear instead of anoutput sun gear.

What I claim is: n

An hydraulic transmission of the type comprising two hydraulic deviceseach having a rotatably mounted nonadjustable cylindrical block, pistonsmovable in said block anda pistons control member to Vmove said pistonswhen said block and said control member are given a rotation movementone relatively to the other, said control member being xed in rotationand adjustable in inclination to control the output of said hydraulicdevice, distributing means iixed in rotation for hydraulicallyconnecting said hydraulic devices, lan input shaft, an output shaft, a

planetary differential gear having niinput sun gear drivingly connectedto said input s'ha'it, aplanet gear carrier drivingly connected to oneof said `cylindrical blocks', a iirst output sun gear. drivinglyconnected to saidroutput shaft, ra second output sun gear drivinglyconnected to the other of said cylindrical blocks, a first group ofdouble planet gears carried by said planet gear carrier andcomprisingeach two drivingly connected gears respectively meshing with said inputsun gearand said second output sun gear, a second group of doubleplanetV gears carried n by said planet gear carrier and comprising eachYtwo drivingly connected Vgears respectively meshing with said rstoutput sun gear and with said gears of said lirst ,group ofl doubleplanet gears meshing with said input sun gear, and

means for simultaneously adjusting the inclination of both said pistonscontrol member.

References' cited inthe meer' this patent UNITED STATES P ATENTS1,197,789 Bluemel -Y sept. 12, 1916 2,580,946 Or'shansky et al .r Jan.1, H52

2,599,814 Cull June 1t), 1952 FOREIGN PATENTS E 10,760 n/sse GermanyFeb. 9, 1956

